Security systems are generally known. Such systems may be used in homes or offices or even in industrial settings to detect intruders.
Many different types of intrusion detectors are in use. In its simplest form, an intrusion detector may simply be an electrical switch that detects an intruder by sensing the unauthorized opening of a door.
In more sophisticated systems, intrusion may be based upon the direct detection of intruders within a protected space. In this regard, many security systems use intrusion detectors based on microwaves and upon a microwave sensing technology that detects the movement of people (objects). However, to ensure the properly functioning of the microwave detectors and its hardware circuit while detecting intrusions, it is often necessary to include a periodic auto-monitoring function (i.e., a self-checking function). If the function finds an abnormality in the microwave module or its hardware circuit, then the function give a warning or reminder of the failure, to notify a user that the detector need to be replaced or repaired. The technical difficulty in such cases becomes the question of how to correctly self-test the microwave intrusion detector without triggering false alarms.